Interferometer using integrated imaging array and high-density polarizer array

Abstract

An integrated imaging element for an interferometer generates at least one image that includes multiple interference portions with different relative phase shifts interleaved in a pattern having a high spatial frequency in the image. The interleaved pattern is at least partially determined by the pattern of a high density polarizing array used in the integrated imaging element. In various embodiments, the multiple interference portions are interleaved in a checkerboard pattern across the entire surface of a detector device. As a result, various non-common mode errors present in various interferometers that generate separate non-interleaved images for each relative phase are reduced or eliminated because multiple phase-shifted interference image information for a small region of an object is provided within a small region on the detector device.

1. An interferometer, comprising:
 a transmitting portion that directs differently polarized portions of a coherent light beam to a reference element and an object, combines the differently polarized portions returned from the reference element and object into a combined wavefront, and outputs the combined wavefront;  
 a multiple phase shift image generating portion arranged to input the combined wavefront, the multiple phase shift image generating portion comprising at least a first polarizer array arranged along at least a first optical path, the first polarizer array comprising a plurality of first polarizing portions having a first polarization direction and a plurality of second polarizing portions having a second polarization direction, the first and second polarizing portions arranged in a pattern within the first polarizer array; and  
 a detector portion comprising at least a first detector array arranged along the first optical path, wherein: 
 the first polarizer array receives at least a sub-wavefront of the combined wavefront including the differently polarized portions;  
 the first polarizing portions transmit the differently polarized portions of the sub-wavefront to produce at least first interference portions, the first interference portions comprising interference light having a first unique phase relationship;  
 the second polarizing portions transmit the differently polarized portions of the sub-wavefront to produce at least second interference portions, the second interference portions comprising interference light having a second unique phase relationship; and  
 the multiple phase shift image generating portion outputs interleaved multiple phase-shifted interference image information from at least the first polarizer array, the interleaved multiple phase-shifted interference image information from the first polarizer array comprising at least the first interference portions and the second interference portions, at least the first interference portions and the second interference portions interleaved at a spatial frequency determined at least partially by the pattern of the first polarizing portions and the second polarizing portions in the first polarizer array.  
 
 
   
   
     2. The interferometer of  claim 1 , wherein the interleaved multiple phase-shifted interference image information from the first polarizer array is output to form an interleaved image on the first detector array. 
   
   
     3. The interferometer of  claim 2 , wherein the at least first interference portions and the at least second interference portions each have nominal extents in the interleaved image on the first detector array, and the nominal extents are nominally aligned to coincide with the boundaries of a coextensive set of pixels of the first detector array. 
   
   
     4. The interferometer of  claim 3 , wherein the coextensive set of pixels on the first detector array is N pixels wide and M pixels high, where M and N are integers. 
   
   
     5. The interferometer of  claim 4 , wherein M is at most equal to 16 and N is at most equal to 16. 
   
   
     6. The interferometer of  claim 5 , wherein M at most equal to 8 and N is at most equal to 8. 
   
   
     7. The interferometer of  claim 1 , wherein the first unique phase relationship corresponds to zero degrees relative phase shift in the corresponding interference light and the second unique phase relationship corresponds to 180 degrees relative phase shift in the corresponding interference light. 
   
   
     8. The interferometer of  claim 1 , wherein the pattern of the plurality of first polarizing portions and the plurality of second polarizing portions in the first polarizer array comprises a checkerboard pattern. 
   
   
     9. The interferometer of  claim 1 , wherein the first polarizer array is positioned in proximity to a detector surface of the first detector array. 
   
   
     10. The interferometer of  claim 1 , wherein the multiple phase shift image generating portion further comprises a first retarder element arranged along the first optical path to receive the sub-wavefront of the combined wavefront including the differently polarized portions and to transmit the sub-wavefront to the first polarizer array. 
   
   
     11. The interferometer of  claim 10 , wherein the first retarder element comprises at least one of at least one null phase-shift element and at least one quarter wave phase-shift element. 
   
   
     12. The interferometer of  claim 11 , wherein the first polarizer array is fabricated on a surface of the first retarder element which faces the first detector array and the first polarizer array is positioned in proximity to a detector surface of the first detector array. 
   
   
     13. The interferometer of  claim 10 , wherein at least the first retarder element, the first polarizer array, and the first detector array form an integrated monolithic phase-shift imaging element. 
   
   
     14. The interferometer of  claim 10 , wherein:
 the first retarder element comprises a first phase-shifting array:  
 the first phase-shifting array comprises a plurality of first phase-shift portions providing a first phase shift and a plurality of second phase-shift portions providing a second phase shift, the pluralities of the first and second phase shift portions arranged in a pattern within the first phase-shifting array;  
 the first phase-shifting array is aligned relative the first polarizer array such that each of the first and second polarizing portions are nominally aligned with a single one of the first and second phase-shift portions such that:  
 for the first polarizing portions that are aligned with the first phase-shift portions, the first polarizing portions transmit the differently polarized portions of the sub-wavefront to produce the first interference portions comprising interference light having the first unique phase relationship;  
 for the second polarizing portions that are aligned with the first phase-shift portions, the second polarizing portions transmit the differently polarized portions of the sub-wavefront to produce the second interference portions comprising interference light having the second unique phase relationship;  
 for the first polarizing portions that are aligned with the second phase-shift portions, the first polarizing portions transmit the differently polarized portions of the sub-wavefront to produce a third interference portion comprising interference light having a third unique phase relationship;  
 for the second polarizing portions that are aligned with the second phase-shift portions, the second polarizing portions transmit the differently polarized portions of the sub-wavefront to produce a fourth interference portion comprising interference light having a fourth unique phase relationship; and  
 the multiple phase shift image generating portion outputs interleaved multiple phase-shifted interference image information from at least the first polarizer array, the interleaved multiple phase-shifted interference image information from the first polarizer array comprising the first, second, third and fourth interference portions, the first, second, third and fourth interference portions interleaved at a spatial frequency determined at least partially by the pattern of the first polarizing portions and the second polarizing portions in the first polarizer array in combination with the pattern of the plurality of first phase shift portions and the plurality of second phase-shift portions in the first phase-shifting array.  
 
   
   
     15. The interferometer of  claim 14 , wherein:
 the pattern of the plurality of first polarizing portions and the plurality of second polarizing portions in the first polarizer array comprises a striped polarization pattern;  
 the pattern of the plurality of first phase shift portions and the plurality of second phase-shift portions in the first phase-shifting array comprises a striped retarder pattern; and  
 the striped retarder pattern is nominally orthogonal to the striped polarization pattern.  
 
   
   
     16. The interferometer of  claim 14 , wherein the pattern of the plurality of first polarizing portions and the plurality of second polarizing portions in the first polarizer array comprises a checkerboard polarization pattern and the pattern of the plurality of first phase shift portions and the plurality of second phase-shift portions in the first phase-shifting array comprises a striped retarder pattern. 
   
   
     17. The interferometer of  claim 14 , wherein the pattern of the plurality of first polarizing portions and the plurality of second polarizing portions in the first polarizer array comprises a checkerboard polarization pattern and the pattern of the plurality of first phase shift portions and the plurality of second phase-shift portions in the first phase-shifting array comprises a checkerboard retarder pattern that is coarser than the checkerboard polarization pattern. 
   
   
     18. The interferometer of  claim 14 , wherein the plurality of first phase-shift portions comprise a plurality of null phase-shift portions and the plurality of second phase-shift portions comprise a plurality of quarter wave phase-shift portions. 
   
   
     19. The interferometer of  claim 14 , wherein the first unique phase relationship corresponds to zero degrees relative phase shift in the corresponding interference light, the second unique phase relationship corresponds to 180 degrees relative phase shift in the corresponding interference light, the third unique phase relationship corresponds to 90 degrees relative phase shift in the corresponding interference light, and the fourth unique phase relationship corresponds to 270 degrees relative phase shift in the corresponding interference light. 
   
   
     20. The interferometer of  claim 1 , wherein:
 the multiple phase shift image generating portion further comprises: 
 a beam-splitting surface,  
 a first retarder element useable to provide at least a first phase shift,  
 a second retarder element useable to provide at least a second phase shift, and  
 a second polarizer array arranged along a second optical path, the second polarizer array comprising a plurality of first polarizing portions having the first polarization direction and a plurality of second polarizing portions having the second polarization direction, the first and second polarizing portions arranged in a pattern within the second polarizer array;  
 
 the detector portion further comprises a second detector array arranged along the second optical path,  
 the beam-splitting surface is arranged to receive the combined wavefront and to transmit a first sub-wavefront of the combined wavefront including the differently polarized portions along the first optical path and a second sub-wavefront of the combined wavefront including the differently polarized portions along the second optical path;  
 the first retarder element is arranged along the first optical path to receive the first sub-wavefront and transmit the first sub-wavefront to the first polarizer array;  
 the second retarder element is arranged along the second optical path to receive the second sub-wavefront and transmit the second sub-wavefront to the second polarizer array;  
 the first polarizing portions of the first polarizer array transmit the differently polarized portions of the first sub-wavefront to produce at least the first interference portions that comprises the interference light having the first unique phase relationship;  
 the second polarizing portions of the first polarizer array transmit the differently polarized portions of the first sub-wavefront to produce at least the second interference portions that comprises the interference light having the second unique phase relationship;  
 the first polarizing portions of the second polarizer array transmit the differently polarized portions of the second sub-wavefront to produce at least third interference portions, the third interference portions comprising interference light having a third unique phase relationship;  
 the second polarizing portions of the second polarizer array transmit the differently polarized portions of the second sub-wavefront to produce at least fourth interference portions, the fourth interference portions comprising interference light having a fourth unique phase relationship; and  
 the multiple phase shift image generating portion further outputs interleaved multiple phase-shifted interference image information from the second polarizer array, the interleaved multiple phase-shifted interference image information from the second polarizer array comprising the at least third interference portions and the at least fourth interference portions, the at least third interference portions and the at least fourth interference portions interleaved at a spatial frequency determined at least partially by the pattern of the first polarizing portions and the second polarizing portions in the second polarizer array.  
 
   
   
     21. The interferometer of  claim 20 , wherein:
 the interleaved multiple phase-shifted interference image information from the first polarizer array is output to form a first interleaved image on the first detector array;  
 the interleaved multiple phase-shifted interference image information from the second polarizer array is output to form a second interleaved image on the second detector array; and  
 the second interleaved image corresponds to the first interleaved image.  
 
   
   
     22. The interferometer of  claim 21 , wherein the first, second, third and fourth interference portions each have nominal extents in corresponding interleaved images on the corresponding detector arrays, and the nominal extents are nominally aligned to coincide with the boundaries of coextensive sets of pixels of the corresponding detector arrays, and the coextensive set of pixels are each N pixels wide and M pixels high, where M and N are integers at most equal to 16. 
   
   
     23. The interferometer of  claim 20 , wherein the first unique phase relationship corresponds to zero degrees relative phase shift in the corresponding interference light, the second unique phase relationship corresponds to 180 degrees relative phase shift in the corresponding interference light, the third unique phase relationship corresponds to 90 degrees relative phase shift in the corresponding interference light, and the fourth unique phase relationship corresponds to 270 degrees relative phase shift in the corresponding interference light. 
   
   
     24. The interferometer of  claim 20 , wherein:
 the first retarder element comprises a null phase-shift element; and  
 the second retarder element comprises a quarter wave phase-shift element.  
 
   
   
     25. The interferometer of  claim 24 , wherein:
 the pattern of the plurality of first polarizing portions and the plurality of second polarizing portions in the first polarizer array comprises a checkerboard pattern; and  
 the pattern of the plurality of first polarizing portions and the plurality of second polarizing portions in the second polarizer array comprises a similar checkerboard pattern.  
 
   
   
     26. The interferometer of  claim 20 , wherein:
 the multiple phase shift image generating portion further comprises a first reflective surface and a second reflective surface;  
 the first reflective surface is arranged to receive the first sub-wavefront from the beam splitting surface and reflect the first sub-wavefront along a portion of the first optical path that extends along a first direction;  
 the second reflective surface is arranged to receive the second sub-wavefront from the beam splitting surface and reflect the second sub-wavefront along a portion of the second optical path that is parallel to the first direction;  
 the first retarder element and the second retarder element are nominally coplanar;  
 the first polarizer array and the second polarizer array are nominally coplanar; and  
 the first detector array and the second detector array are nominally coplanar.  
 
   
   
     27. The interferometer of  claim 26 , wherein at least one of a) the set of the first retarder element and the second retarder element, b) the set of the first polarizer array and the second polarizer array, and c) the set of the first detector array and the second detector array comprise first and second portions of the same element. 
   
   
     28. The interferometer of  claim 20 , wherein at least the elements of the multiple phase shift image generating portion and the first detector array form an integrated phase-shift imaging element. 
   
   
     29. The interferometer of  claim 1 , wherein the plurality of first polarizing portions and the plurality of second polarizing portions comprise wire-grid polarizers. 
   
   
     30. A method for determining a distance using an interferometer, comprising:
 directing differently polarized portions of a coherent light beam to a reference element and an object;  
 combining the differently polarized portions returned from the reference element and object into a combined wavefront;  
 passing the combined wavefront through at least a first polarizer array arranged along at least a first optical path, the first polarizer array comprising a plurality of first polarizing portions having a first polarization direction and a plurality of second polarizing portions having a second polarization direction, the first and second polarizing portions arranged in a pattern within the first polarizer array, to produce interleaved multiple phase-shifted interference image information, comprising: 
 receiving at the first polarizer array at least a sub-wavefront of the combined wavefront including the differently polarized portions,  
 transmitting through the first polarizing portions the differently polarized portions of the sub-wavefront to produce at least first interference portions, the first interference portions comprising interference light having a first unique phase relationship,  
 transmitting through the second polarizing portions the differently polarized portions of the sub-wavefront to produce at least second interference portions, the second interference portions comprising interference light having a second unique phase relationship; and  
 
 directing the interleaved multiple phase-shifted interference image information from at least the first polarizer array to a detector portion comprising at least a first detector array arranged along the first optical path;  
 wherein the interleaved multiple phase-shifted interference image information comprises at least the first interference portions and the at least second interference portions interleaved at a spatial frequency determined at least partially by the pattern of the first polarizing portions and the second polarizing portions in the first polarizer array.  
 
   
   
     31. The method of  claim 30 , wherein directing the interleaved multiple phase-shifted interference image information from at least the polarizer array to a detector portion comprises forming an interleaved image on the first detector array. 
   
   
     32. The method of  claim 31 , wherein:
 the at least first interference portions and the at least second interference portions each have nominal extents in the interleaved image on the first detector array; and  
 forming the interleaved image on the first detector array comprises projecting at least the interleaved first and second interference portions onto the first detector array such that the nominal extents nominally coincide with the boundaries of a coextensive set of pixels of the first detector array.  
 
   
   
     33. The method of  claim 32 , wherein the coextensive set of pixels on the first detector array is N pixels wide and M pixels high, where M and N are integers and M is at most equal to 16 and N is at most equal to 16. 
   
   
     34. The method of  claim 30 , wherein the pattern of the plurality of first polarizing portions and the plurality of second polarizing portions in the first polarizer array comprises a checkerboard pattern. 
   
   
     35. The method of  claim 30 , wherein:
 the multiple phase shift image generating portion further comprises a first retarder element arranged along the first optical path;  
 passing the combined wavefront through at least a first polarizer array arranged along at least the first optical path further comprises: 
 receiving at the first retarder element the sub-wavefront of the combined wavefront including the differently polarized portions, and  
 transmitting the sub-wavefront to the first polarizer array and  
 
 receiving at the first polarizer array at least the sub-wavefront of the combined wavefront comprises receiving the sub-wavefront transmitted from the retarder element.  
 
   
   
     36. The method of  claim 35 , wherein the first retarder element comprises at least one of at least one null phase-shift element and at least one quarter wave phase-shift element. 
   
   
     37. The method of  claim 35 , wherein:
 the first retarder element comprises a first phase-shifting array that comprises a plurality of first phase-shift portions providing a first phase shift and a plurality of second phase-shift portions providing a second phase shift, the pluralities of the first and second phase shift portions arranged in a pattern within the first phase-shifting array;  
 the first phase-shifting array is aligned relative the first polarizer array such that each of the first and second polarizing portions are nominally aligned with a single one of the first and second phase-shift portions; and  
 transmitting through the first polarizing portions the differently polarized portions of the sub-wavefront comprises: 
 transmitting the differently polarized portions of the sub-wavefront through the first phase-shift portions and the first polarizing portions that are aligned with the first phase-shift portions to produce the first interference portions comprising interference light having the first unique phase relationship, and  
 transmitting the differently polarized portions of the sub-wavefront through the second phase-shift portions and the first polarizing portions that are aligned with the second phase-shift portions to produce a third interference portions comprising interference light having a third unique phase relationship;  
 
 transmitting through the second polarizing portions the differently polarized portions of the sub-wavefront comprises: 
 transmitting the differently polarized portions of the sub-wavefront through the first phase-shift portions and the second polarizing portions that are aligned with the first phase-shift portions to produce the second interference portions comprising interference light having the second unique phase relationship, and  
 transmitting the differently polarized portions of the sub-wavefront through the second phase-shift portions and the second polarizing portions that are aligned with the second phase-shift portions to produce a fourth interference portions comprising interference light having a fourth unique phase relationship; and  
 
 directing the interleaved multiple phase-shifted interference image information from at least the first polarizer array to the detector portion comprises directing the first, second, third and fourth interference portions to the detector portion; wherein at least the first, second, third and fourth interference portions are interleaved at a spatial frequency determined at least partially by the pattern of the first polarizing portions and the second polarizing portions in the first polarizer array in combination with the pattern of the plurality of first phase shift portions and the plurality of second phase-shift portions in the first phase-shifting array.  
 
   
   
     38. The method of  claim 37 , wherein the first unique phase relationship corresponds to zero degrees relative phase shift in the corresponding interference light, the second unique phase relationship corresponds to 180 degrees relative phase shift in the corresponding interference light, the third unique phase relationship corresponds to 90 degrees relative phase shift in the corresponding interference light, and the fourth unique phase relationship corresponds to 270 degrees relative phase shift in the corresponding interference light. 
   
   
     39. A method for determining a distance using an interferometer, comprising:
 directing differently polarized portions of a coherent light beam to a reference element and an object;  
 combining the differently polarized portions returned from the reference element and object into a combined wavefront;  
 splitting the combined wavefronts into at least a first sub-wavefront of the combined wavefront including the differently polarized portions and a second sub-wavefront of the combined wavefront including the differently polarized portions;  
 directing the first sub-wavefront along a first optical path to a first retarder element;  
 directing the second sub-wavefront along a second optical path to a second retarder element;  
 passing the first sub-wavefront through the first retarder element and a first polarizer array to produce first interleaved multiple phase-shifted interference image information, wherein: 
 the first retarder element provides at least a first phase shift, and  
 the first polarizer array comprises a plurality of first polarizing portions having a first polarization direction and a plurality of second polarizing portions having a second polarization direction, the first and second polarizing portions arranged in a pattern within the first polarizer array,  
 
 comprising: 
 receiving at the first polarizer array the first sub-wavefront of the combined wavefront including the differently polarized portions having the first phase shift,  
 transmitting through the first polarizing portions the differently polarized portions having the first phase-shift of the first sub-wavefront to produce at least first interference portions comprising interference light having a first unique phase relationship, and  
 transmitting through the second polarizing portions the differently polarized portions having the first phase shift of the first sub-wavefront to produce at least second interference portions comprising interference light having a second unique phase relationship;  
 
 passing the second sub-wavefront through the second retarder element and a second polarizer array to produce second interleaved multiple phase-shifted interference image information, wherein: 
 the second retarder element provides at least a second phase shift, and  
 the second polarizer array comprising a plurality of first polarizing portions having the first polarization direction and a plurality of second polarizing portions having the second polarization direction, the first and second polarizing portions arranged in a pattern within the second polarizer array,  
 
 comprising: 
 receiving at the second polarizer array the second sub-wavefront of the combined wavefront including the differently polarized portions having the second phase shift,  
 transmitting through the first polarizing portions the differently polarized portions having the second phase-shift of the second sub-wavefront to produce at least third interference portions comprising interference light having a third unique phase relationship, and  
 transmitting through the second polarizing portions the differently polarized portions having the second phase shift of the second sub-wavefront to produce at least fourth interference portions comprising interference light having a fourth unique phase relationship;  
 
 directing the first interleaved multiple phase-shifted interference image information onto a first detector array; and  
 directing the second interleaved multiple phase-shifted interference image information onto a second detector array;  
 wherein: 
 the first interleaved multiple phase-shifted interference image information comprises at least the first interference portions and the second interference portions interleaved at a spatial frequency determined at least partially by the pattern of the first polarizing portions and the second polarizing portions in the first polarizer array; and  
 the second interleaved multiple phase-shifted interference image information comprises at least the third interference portions and the fourth interference portions interleaved at a spatial frequency determined at least partially by the pattern of the first polarizing portions and the second polarizing portions in the second polarizer array.  
 
 
   
   
     40. The method of  claim 39 , wherein:
 directing the first interleaved multiple phase-shifted interference image information onto the first detector array comprises forming a first interleaved image on the first detector array;  
 directing the second interleaved multiple phase-shifted interference image information onto the second detector array comprises forming a second interleaved image on the second detector array; and  
 the second interleaved image corresponds to the first interleaved image.  
 
   
   
     41. The method of  claim 40 , wherein:
 the at least first interference portions and the at least second interference portions each have nominal extents in the first interleaved image on the first detector array;  
 the at least third interference portions and the at least fourth interference portions each have nominal extents in the second interleaved image on the second detector array;  
 forming the first interleaved image on the first detector array comprises projecting at least the interleaved first and second interference portions onto the first detector array such that the nominal extents nominally coincide with the boundaries of a coextensive set of pixels of the first detector array;  
 forming the second interleaved image on the second detector array comprises projecting at least the interleaved third and fourth interference portions onto the second detector array such that the nominal extents nominally coincide with the boundaries of a coextensive set of pixels of the second detector array and 
 the coextensive set of pixels are each N pixels wide and M pixels high, where M and N are integers at most equal to 16.  
 
 
   
   
     42. The method of  claim 39 , wherein the first unique phase relationship corresponds to zero degrees relative phase shift in the corresponding interference light, the second unique phase relationship corresponds to 180 degrees relative phase shift in the corresponding interference light, the third unique phase relationship corresponds to 90 degrees relative phase shift in the corresponding interference light, and the fourth unique phase relationship corresponds to 270 degrees relative phase shift in the corresponding interference light. 
   
   
     43. The method of  claim 39 , wherein:
 the first retarder element comprises a null phase-shift element; and  
 the second retarder element comprises a quarter wave phase-shift element.  
 
   
   
     44. The method of  claim 43 , wherein:
 the pattern of the plurality of first polarizing portions and the plurality of second polarizing portions in the first polarizer array comprises a checkerboard pattern; and  
 the pattern of the plurality of first polarizing portions and the plurality of second polarizing portions in the second polarizer array comprises a similar checkerboard pattern.  
 
   
   
     45. The method of  claim 39 , wherein:
 directing the first sub-wavefront along the first optical path to the first retarder element comprises: 
 directing the first sub-wavefront to a first reflective surface, and  
 directing the first sub-wavefront from the first reflective surface to the first retarder element along a portion of the first optical path that extends along a first direction;  
 
 directing the second sub-wavefront along the second optical path to the second retarder element comprises: 
 directing the second sub-wavefront to a second reflective surface, and  
 directing the second sub-wavefront from the second reflective surface to the second retarder element along a portion of the second optical path that that is parallel to the first direction; wherein:  
 
 the first retarder element and the second retarder element are nominally coplanar;  
 the first polarizer array and the second polarizer array are nominally coplanar; and  
 the first detector array and the second detector array are nominally coplanar.